1. Field of the Invention
This invention relates to a pitch fluoride and a process for preparing the same. More particularly, the present invention is concerned with a pitch fluoride, which is a novel carbon fluoride having various excellent properties comparable or superior to those of conventionally known graphite fluorides. This invention is also concerned with a novel solid fluoro compound which is produced by the thermal decomposition of a pitch fluoride and which not only has various excellent properties comparable or superior to those of conventionally known graphite fluorides but also is capable of forming a film by vacuum deposition. The present invention is further concerned with a novel film having excellent properties which can be produced from the above-mentioned pitch fluoride or solid fluoro compound.
2. Discussion Of Related Art
Recenty, a graphite fluoride prepared by the direct fluorination of a carbon material having a relatively well developed graphite structure, such as natural graphite or heat-treated coke, has been drawing attention as a new industrial material because of its unique properties. For example, poly-monocarbon monofluoride represented by the formula (CF).sub.n is well known as one of the graphite fluorides. (CF).sub.n is a solid powder material having excellent lubricating and water- and oil-repellent properties as well as excellent chemical resistance. Therefore, (CF).sub.n has been used as a solid lubricant, and also used as anti-wetting, stain-resistant and water- and oil-repellent materials. Further, (CF).sub.n has been used as an active material capable of providing a primary cell of high energy density and long shelf life in which voltage drop due to discharge is scarcely observed for a long period of time as disclosed in U.S. Pat. No. 3,536,532.
Poly-dicarbon monofluoride represented by the formula (C.sub.2 F).sub.n which was found by Watanabe et al. has almost the same properties as (CF).sub.n, and is highly appreciated in a wide variety of industrial fields (see, for example, U.S. reissued Pat. No. Re 30,667).
However, both of the above-mentioned graphite fluorides, i.e. (CF).sub.n and (C.sub.2 F).sub.n, have problems with respect to the production thereof. Specifically, the thermal decomposition temperature of (CF).sub.n is extremely close to the temperature employed for the formation of the (CF).sub.n. In general, the temperature difference between the formation temperature of (CF).sub.n and the decomposition temperature is only about 10 to about 50.degree. C. and, therefore, strict control of the reaction temperature is required. Moreover, since both the formation reaction and decomposition reaction of (CF).sub.n are exothermic, the temperature control is so difficult that the formation reaction and decomposition reaction tend to occur at the same time, and this prevents (CF).sub.n from being stably produced in high yield. Therefore, for the purpose of improving the yield of (CF).sub.n, it has been attempted to effect the fluorination reaction in multiple steps. This makes the manufacturing process complicated and unpractical. Further, when (CF).sub.n is produced using a natural graphite or an artificial graphite as a starting material, it is necessary to react the graphite with fluorine, which is a highly corrosive gas, at a temperature as high as about 500.degree. to 630.degree. C. and, therefore, a reaction vessel to be used in the reaction must be made of an expensive material, such as nickel, and this also makes the process uneconomical.
With respect to the formation of poly-dicarbon monofluoride (C.sub.2 F).sub.n, although the reaction temperature is lower than that for forming (CF).sub.n, it is still necessary to conduct the reaction at relatively high temperatures, namely, 300.degree. to 500.degree. C., so that the use of a reaction vessel of an expensive material, such as nickel, is needed as in the case of formation of (CF).sub.n. Further, in the formation of (C.sub.2 F).sub.n, the use of highly crystallized graphite material is required. For example, in the case where petroleum cokes are employed, they must be used after heat-treated for enhancing crystallinity thereof. In addition to the above-mentioned drawbacks, (C.sub.2 F).sub.n has such a disadvantage that the reaction time required for the production thereof is long.